How Do You Feel? brings together startling evidence from neuroscience, psychology, and psychiatry to present revolutionary new insights into how our brains enable us to experience the range of sensations and mental states known as feelings. Drawing on his own cutting-edge research, neurobiologist Bud Craig has identified an area deep inside the mammalian brain-the insular cortex-as the place where interoception, or the processing of bodily stimuli, generates feelings. He shows how this crucial pathway for interoceptive awareness gives rise in humans to the feeling of being alive, vivid perceptual feelings, and a subjective image of the sentient self across time. Craig explains how feelings represent activity patterns in our brains that signify emotions, intentions, and thoughts, and how integration of these patterns is driven by the unique energy needs of the hominid brain. He describes the essential role of feelings and the insular cortex in such diverse realms as music, fluid intelligence, and bivalent emotions, and relates these ideas to the philosophy of William James and even to feelings in dogs.How Do You Feel? is also a compelling insider's account of scientific discovery, one that takes readers behind the scenes as the astonishing answer to this neurological puzzle is pursued and pieced together from seemingly unrelated fields of scientific inquiry. This book will fundamentally alter the way that neuroscientists and psychologists categorize sensations and understand the origins and significance of human feelings.
List of Figures and Plates ixList of Boxes xiPreface xiii1AN INTRODUCTION TO INTEROCEPTION 12FEELINGS FROM THE BODY VIEWED AS EMOTIONSIdeas from the lamina I projection map that add to the textbooks 16An overview of the map 16The central neural substrates for homeostasis 19Textbook knowledge regarding touch 23Textbook knowledge regarding pain and temperature 28Irritating incongruities 31Identification of the thermosensory pathway 33Recognizing that temperature sensation is part of interoception 38Viewing a thermosensory feeling as a homeostatic emotion 42Thermal sensations become subjective feelings 45Emergent ideas about feelings, moments, music, and time 46Bivalent emotions in bicameral brains 503THE ORIGIN OF THE INTEROCEPTIVE PATHWAYHomeostatic sensory fibers and the interoceptive dorsal horn 54Finding lamina I spinothalamic neurons 55Lamina I spinothalamic neurons are "labeled lines 62Anomalous characteristics point to a new direction 71Integrated lamina I activity generates thermoregulatory pain: the thermal grill 74Identifying lamina I projections to autonomic neurons 82Demonstrating that lamina I subserves homeostasis 90The identification of homeostatic small-diameter sensory fibers 94The development of the interoceptive dorsal horn 97The interoceptive dorsal horn subserves homeostasis 101The evolutionary origin of interoceptive and exteroceptive neurons 103The homeostatic sensory system provides crucial vasoreceptive feedback 1064INTEROCEPTION AND HOMEOSTASISLamina I terminations at cardiorespiratory sites in the brainstem 111An overview of lamina I projections to the brainstem 112Lamina I terminations in the lower brainstem (medulla) 115Lamina I terminations in the middle brainstem (pons) 118Lamina I terminations in the parabrachial nucleus 119Lamina I terminations in the periaqueductal gray (upper brainstem) 124Summary 1295THE INTEROCEPTIVE PATHWAY TO THE INSULAR CORTEXLamina I spinothalamic input to the thalamus and cortex in primates 130My introduction to functional neuroanatomy 131The significance of somatotopic organization 133The lateral spinothalamic tract 134Finding Waldo 135The functional anatomical characteristics of the VMpo in the macaque monkey 139The projection from the VMpo to the dorsal posterior insula in the macaque monkey 145The organization of the dorsal posterior insula in the macaque monkey 150The interoceptive pathway 155The human VMpo 160The human dorsal posterior insula 166The human interoceptive cortex 170Interoceptive touch 173Summary, and an interoceptive perspective on cortical gyrification 1756BODILY FEELINGS EMERGE IN THE INSULAR CORTEXInteroceptive integration generates the feeling of being alive 182The structure of the insular cortex 183Posterior-to-mid-to-anterior processing of interoceptive activity 185Multimodal integration in the mid-insula 188Feelings from the body emerge first in the mid-insula 191Homeostatic sentience 194Interoceptive integration improves energy efficiency 197The model of interoceptive integration and the generalization of feelings 199Interoceptive feelings come to awareness in the anterior insula 203Emotional feelings emerge and come to awareness in the anterior insula 206The embodiment of emotional feelings 2097FEELINGS ABOUT THOUGHTS, TIME, AND MEAwareness emerges in the anterior insular cortex 216The AIC is activated during cognitive activity 219The model: Integration of cognitive feelings 221Evidence that awareness is engendered in the AIC 223Evidence that the AIC supports feelings about time 226The model: Cinemascopic integration of moments of time 228The model: The structural basis of awareness 235The role of the AIC in the control of network activity 243Evidence that the AIC is crucial for fluid intelligence 247Evidence that the AIC optimizes energy utilization 249Individual variability and maturation 251Distorted feelings produce mental illness 2548FEELINGS AND EMOTIONS ON BOTH SIDES OF THE BRAINThe asymmetric forebrain 257Ethological evidence of forebrain asymmetry 260Neuroanatomical evidence of forebrain and AIC asymmetry 262Clinical evidence of forebrain and AIC asymmetry 263Physiological evidence of forebrain and AIC asymmetry 265Psychophysiological evidence of forebrain and AIC asymmetry 267Two recent reviews uncover asymmetric activation of the amygdala and the AIC 270The alignment of autonomic, behavioral, and affective control 272Opponent inhibition 274Specialization and balance 275And something curious 2779A FEW MORE THOUGHTS ABOUT FEELINGSGraded sentience and tail-wagging in dogs 280A quick review 280Scaling up homeostatic sentience 285Graded sentience 289Feelings in dogs 293How about Watson? 295Acknowledgments 297Abbreviations 299Glossary 301Reference List 309Illustration Credits 337Index 339